Effect of gums on the rheological characteristics and microstructure of acid-induced SPI-gum mixed gels

• Rheological behavior and microstructure of SPI-gum mixtures were studied.
• Addition of gums significantly increased the viscosity of the SPI-gum solutions.
• G′ and G″ of SPI-gum gels increased with the increase in gum (XG, GG) concentration.
• Presence and increase in gum concentration greatly affected gels’ microstructure.
• Number density of protein aggregates in mixed gels increased with gum concentration.

The effect of addition of xanthan gum (XG) and guar gum (GG) on the rheological properties and microstructure of glucono-δ-lactone induced soy protein isolate (SPI)-XG gels and SPI-GG gels was investigated using steady and dynamic rheological tests, creep-recovery and confocal laser scanning microscopy (CLSM). Results showed that the apparent viscosity of SPI-gum (XG, GG) mixed solutions increased with the increase in the gum (XG, GG) concentration. The storage (G′) and loss (G″) moduli of SPI-gum (XG, GG) mixed gels increased in the presence and increase in the gum (XG, GG) concentration. The Burger's model fitted the creep recovery data well (R2 > 0.919) and showed that both the instantaneous and equilibrium (retarded) elastic components of this model increased with the increase in SPI and gum concentrations. The proportion occupied by gum in mixed gels was found to increase with the increase in the concentration of gums which increased the density of protein aggregates in the mixed gels.